1. Field of the Invention
This invention pertains to locking apparatus, and more particularly to apparatus for locking a mobile filing and storage unit in a predetermined position.
2. Description of the Prior Art
To obtain the maximum use of expensive building space, it is well known to employ mobile filing and storage systems. For example, mobile book shelves are commonly employed in libraries.
A common method of supporting mobile storage units includes wheels that roll on rails embedded in the building floor. The wheels are usually driven through a suitable mechanism by an electric motor or by a chain and sprocket and a manually operated handwheel located on the outside of the shelf.
Typically, mobile shelving units roll very freely. Even a slight and unintended force, such as caused by uneven rails or jarring, can cause a mobile shelf to start moving. Accidental start-up can be dangerous to a person caught between adjacent shelves and can damage the shelf and its contents if it strikes another object.
To prevent accidental start-up of a mobile shelf, a locking device is required. Locking devices can take several forms, but they usually are employed in conjunction with the manual handwheel. In one well-known design, a spring-loaded cam operated friction mechanism provides the locking force. However, friction devices do not provide positive locking. Further, the cam mechanism can wear with use, thus requiring either adjustment or replacement. In another form of locking device, a locking member is inserted between adjacent teeth of a tooth wheel that rotates with the handwheel. The latter design is exemplified by U.S. Pat. No. 4,138,173, wherein a knob protruding from a storage unit actuates, through an inclined plane arrangement, the locking member. Although that system may function satisfactorily, it requires a large number of parts, some of which are relatively expensive to manufacture. Moreover, the mere positioning of the knob does not indicate whether the locking member is properly engaged or disengaged.
Thus, a need exists for a simple, inexpensive, and long lasting mobile storage system locking apparatus that firmly locks the storage unit in place against unintended movement, and that signals the locked and unlocked conditions.